<!doctype html>
<html>

<head>
    <meta charset="utf-8">
    <title>love</title>
    <link href="favicon.ico" rel="shortcut icon" />
    <style>
        .wrap {
            display: flex;
            height: 600px;
        }
        
        .wrap div:nth-child(1) {
            /* flex-grow 0 不放大 */
            /* flex-shrink 0 不缩小 */
            /* flex-grow flex-shrink flex-basis */
            flex: 0 0 200px;
            background-color: red;
        }
        
        .wrap div:nth-child(2) {
            /* flex: 1 1 auto; */
            flex: auto;
            background-color: green;
        }
        
        .wrap div:nth-child(3) {
            flex: 0 0 200px;
            background-color: blue;
        }
    </style>

</head>

<body>

    <div class="wrap">
        <div>1</div>
        <div>2</div>
        <div>3</div>

    </div>
</body>

</html>